Jul 1, 1996

The July 1995 Heat Wave in the Midwest: A Climatic Perspective and Critical Weather Factors

by
Kunkel, K. E., S. A. Changnon, B. C. Reinke, and R. W. Arritt
,
Bulletin of the American Meteorological Society
  • States the most notable feature of the great Chicago heat wave of 1995 was the development of very high dewpoint temperature (Td) over the southern Great Lakes region and the Upper Mississippi River Basin—at many locations, hourly values of Td set new records
  • States the combination of high air and dewpoint temperatures resulted in daily average apparent temperatures exceeding 36°C over a large area on some days
  • Show—using a comparison with past heat waves—that this was the most intense short-duration heat wave in at least the last 48 years at some locations in the southern Great Lakes region and Upper Mississippi River Basin
  • Analyses historical data for Chicago, where the majority of fatalities occurred, and finds the intensity of the Chicago heat wave was exceeded only by a few periods in the 1910s and 1930s
  • Finds the impacts in the Chicago urban center were exacerbated by an urban heat island that raised nocturnal temperatures by more than 2°C
  • Analyses radiosonde data which indicates that maximum daytime boundary layer mixing depths were only a few hundred meters in the core region of the heat wave
  • Finds that simulations strongly suggest that the boundary  layer mixing depths contributed to the very high values of Td since soil moisture in the central United States was near to above average and evapotransporation was likely high, causing a rapid moistening of the shallow boundary layer